Thermotolerance,cell filamentation,and induced protein synthesis in psychrophilic and psychrotrophic bacteria

Both the psychrophile Aquaspirillum arcticum and the psychrotroph Bacillus psychrophilus were found to acquire thermotolerance when either heat shocked or treated with nalidixic acid; two conditions which also resulted in the induction of heat shock proteins and/or stress proteins and also cell filamentation. The possible relatedness of acquisition of thermotolerance and cell filamentation was examined by inhibiting cell filamentation with 1.5% KCl. A. arcticum cells which were heat shocked in the presence of KCl did not become filamentous nor acquire thermotolerance suggesting that these two responses may be related. On the other hand, when cells of B. psychrophilus were treated in a similar fashion, they also were prevented from cell filamentation but their ability to become thermotolerant was unaffected. When A. arcticum cells were heat shocked in the presence of chloramphenicol, heat shock protein synthesis was inhibited but not the acquistion of thermotolerance. Similar experiments with B. psychrophilus revealed that partial induction of heat shock proteins still occurred; however, no thermotolerance was exhibited.Abbreviations hsp(s) heat shock proteins(s) - SEM standard error of the mean     

New observations on the significance of nipplelike protrusions in the nuclei of endocervical cells

Nuclear nippling was noted in the endocervical columnar cells in smears taken from women of child-bearing age who were using a progesterone-only contraceptive. The phenomenon occurred most consistently in smears from women who were amenorrheic, a condition indicative of a marked decrease of estrogen activity. These observations do not support the previous explanations linking nuclear nippling to estrogenic stimulation. Close observation of the progress of these nuclear protrusions showed that they represented an arrested attempt at nuclear division, with the inhibition possibly due to the rapid rise of the progestogen level, which may be caused either by the use of progesterone-only contraceptives or by the onset of ovulation. The presence of nuclear nippling in normal smears may thus establish the occurrence of ovulation; its observation in metastatic tumors should indicate that the primary tumor has a columnar cell component.     

Phylogenetic diversity of subsurface marine microbial communities from the Atlantic and Pacific Oceans.

The extent of the diversity of marine prokaryotes is not well known, primarily because of poor cultivability. However, new techniques permit the characterization of such organisms without culturing, via 16S rRNA sequences obtained directly from biomass. We performed such an analysis by polymerase chain reaction amplification with universal primers on five oligotrophic open-ocean samples: from 100-m (three samples) and 500-m depths in the western California Current (Pacific Ocean) and from a 10-m depth in the Atlantic Ocean near Bermuda. Of 61 clones, 90% were in clusters of two or more related marine clones obtained by ourselves or others. We report 15 clones related to clone SAR 11 found earlier near Bermuda (S. J. Giovannoni, T. B. Britschgi, C. L. Moyer, and K. G. Field, Nature [London] 345:60-63, 1990), 11 related to marine cyanobacteria, 9 clustered in a group affiliated with gram-positive bacteria, 9 in an archaeal cluster we recently described (mostly from the 500-m sample), 4 in a novel gamma-proteobacterial cluster, and 6 in three two-membered clusters (including other archaea). One clone was related to flavobacteria. Only the cyanobacteria plus one other clone, related to Roseobacter denitrificans (formerly Erythrobacter longus Och114), were within 10% sequence identity to any previously sequenced cultured organism in a major data base. We never found more than two occurrences of the same sequence in a sample, although four times we found identical sequences between samples, two of which were between oceans; one of these sequences was also identical to SAR 11.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detecting disease and parasite threats to endangered species and ecosystems

Ecologists have recently begun to acknowledge the importance of disease and parasites in the dynamics of populations. Diseases and parasites have probably been responsible for a number of extinctions on islands and on large land masses, but the problem has only been identified in retrospect. In contrast, endemic pathogens and parasites may operate as keystone species, playing a crucial role in maintaining the diversity of ecological communities and ecosystems. Will recent advances in the understanding of parasite population biology allow us to predict threats to endangered species and communities?     

The role of reactive oxygen species in the virulence of wheat leaf rust fungus Puccinia triticina

Reactive oxygen species (ROS) play an important role during host–pathogen interactions and are often an indication of induced host defence responses. In this study, we demonstrate for the first time that Puccinia triticina (Pt) generates ROS, including superoxide, H₂O₂ and hydroxyl radicals, during wheat infection. Through pharmacological inhibition, we found that ROS are critical for both Pt urediniospore germination and pathogenic development on wheat. A comparative RNA-Seq analysis of different stages of Pt infection process revealed 291 putative Pt genes associated with the oxidation–reduction process. Thirty-seven of these genes encode known proteins. The expressions of five Pt genes, including PtNoxA, PtNoxB, PtNoxR, PtCat and PtSod, were subsequently verified using RT-qPCR analysis. The results show that the expressions of PtNoxA, PtNoxB, PtNoxR, PtCat and PtSod are up-regulated during urediniospore germination. In comparison, the expressions of PtNoxA, PtNoxB, PtNoxR and PtCat are down-regulated during wheat infection from 12 to 120 h after inoculation (HAI), whereas the expression of PtSod is up-regulated with a peak of expression at 120 HAI. We conclude that ROS are critical for the full virulence of Pt and a coordinate down-regulation of PtNox genes may be important for successful infection in wheat.     

Identification and mapping of leaf, stem and stripe rust resistance quantitative trait loci and their interactions in durum wheat

Leaf rust (Puccinia triticina Eriks.), stripe rust (Puccinia striiformis f. tritici Eriks.) and stem rust (Puccinia graminis f. sp. tritici) cause major production losses in durum wheat (Triticum turgidum L. var. durum). The objective of this research was to identify and map leaf, stripe and stem rust resistance loci from the French cultivar Sachem and Canadian cultivar Strongfield. A doubled haploid population from Sachem/Strongfield and parents were phenotyped for seedling reaction to leaf rust races BBG/BN and BBG/BP and adult plant response was determined in three field rust nurseries near El Batan, Obregon and Toluca, Mexico. Stripe rust response was recorded in 2009 and 2011 nurseries near Toluca and near Njoro, Kenya in 2010. Response to stem rust was recorded in field nurseries near Njoro, Kenya, in 2010 and 2011. Sachem was resistant to leaf, stripe and stem rust. A major leaf rust quantitative trait locus (QTL) was identified on chromosome 7B at Xgwm146 in Sachem. In the same region on 7B, a stripe rust QTL was identified in Strongfield. Leaf and stripe rust QTL around DArT marker wPt3451 were identified on chromosome 1B. On chromosome 2B, a significant leaf rust QTL was detected conferred by Strongfield, and at the same QTL, a Yr gene derived from Sachem conferred resistance. Significant stem rust resistance QTL were detected on chromosome 4B. Consistent interactions among loci for resistance to each rust type across nurseries were detected, especially for leaf rust QTL on 7B. Sachem and Strongfield offer useful sources of rust resistance genes for durum rust breeding.